Microelectromechanical systems (MEMS) are very small machines (on the scale of a few micrometers to about ten millimeters) that are produced using modified semiconductor device fabrication technologies, such as photolithography, etching, and thin film deposition. Current MEMS devices include, inter alia, miniature scanning mirrors for use in optical projection and sensing.
For example, U.S. Pat. No. 7,952,781, whose disclosure is incorporated herein by reference, describes a method of scanning a light beam and a method of manufacturing a microelectromechanical system (MEMS), which can be incorporated in a scanning device. Other methods for fabrication of MEMS scanning devices are described in PCT International Publication WO 2014/064606, which is also incorporated herein by reference.
U.S. Patent Application Publication 2013/0207970, whose disclosure is incorporated herein by reference, describes a scanning depth engine, which includes a transmitter, which emits a beam comprising pulses of light, and a scanner, which is configured to scan the beam, within a predefined scan range, over a scene. The scanner may comprise a micromirror produced using MEMS technology. A receiver receives the light reflected from the scene and generates an output indicative of the time of flight of the pulses to and from points in the scene. A processor is coupled to control the scanner and to process the output of the receiver so as to generate a 3D map of the scene.
Another time-of-flight scanner using MEMS technology is the Lamda scanner module produced by the Fraunhofer Institute for Photonic Microsystems IPMS (Dresden, Germany). The Lamda module is constructed based on a segmented MEMS scanner device consisting of identical scanning mirror elements. A single scanning mirror of the collimated transmit beam oscillates parallel to a segmented scanning mirror device of the receiver optics.
PCT International Publication WO 2014/016794, whose disclosure is incorporated herein by reference, describes dual-axis MEMS scanning mirrors and magnetic driving arrangements for such mirrors. In the disclosed embodiments, a micromirror is mounted on a miniature gimbaled base, so that the base rotates relative to a support structure in the low-frequency (slow) scan direction, while the micromirror itself rotates relative to the base in the high-frequency (fast) scan direction. The micromirror assembly is produced by suitably etching a semiconductor substrate to separate the micromirror from the base and to separate the base from the remaining substrate, which serves as the support structure. The same magnetic drive can be used to power both the fast and slow scans.
U.S. Patent Application Publication 2014/0153001, whose disclosure is incorporated herein by reference, describes a gimbaled scanning mirror array, in which a substrate is etched to define an array of two or more parallel micromirrors and a support surrounding the micromirrors. Respective spindles connect the micromirrors to the support, thereby defining respective parallel axes of rotation of the micromirrors relative to the support. One or more flexible coupling members are connected to the micromirrors so as to synchronize an oscillation of the micromirrors about the respective axes.